You will get more suggestions as you continue to respond, but please let us know the outcome because you WILL Find the solution that will help a lot of folks on this forum. Including Me.
.

But? Obviously, SOME here, BUILDING INSPECTORS EVEN, as well as a few DIY homehandy men, "appear' to be vastly more skill trained than A "mere" Industrial Electrician ((whom graduated WITH HONOURS)) so- go fry yourselves..
I don't care.
.
All I care about- is the 1st precaution in that PDF that PaliBob submitted... BUT NONE OF YOU READ.

This document is written for qualified electricians. Other than connecting
and disconnecting receptacle loads, the work described here should be
done only by trained professionals.

Failure to follow these instructions will result in death or

serious injury.

READ THE LINE- it says "WILL" KILL"

Not "maybe"
Not "oh - can I tease?
Can I "bypass"?

CAN I DISOBEY ALL SAFETY ADVICE?
?

The thread starter said a PROTECTION DEVICE FAILED.?
& asked for help.

THE PRECAUTIONS GIVEN WITH THESE UNITS...
specifically say- FIND THE FAULT-

BEFORE RE-POWERING THE CIRCIUIT..

There ARE no 2nd chances... Uv had it.

The protection "tripped".

DO NOT thinK? Oh? I can tease a "sw" (after U were told a fault exists) NOR to "bypass_this" ? with a "piece" of non_protection wire? & Simply being "able" to do an inspection of the building- for "overviews" does NOT imply U know what to look for- UNLESS U are a fully HIGHLY qualified Electrical Inspector, (& even they die- when they "GET IT WRONG").

DO NOT PLAY.
If the device trips. LEAVE THE CIRCUIT DEAD & fault find the CORRECT WAY.

As to house fires, dividing your fire insurance premium by the replacement value of your house will approximate the likelihood of a house fire for any reason, per year.

It should be impossible to tease a good switch; there is a built-in snap action, the effect being the same as what hysteresis gives you.

P.s
U "forgot" the 100% death rate- at the END of any "life".
So it does NOT matter what statistic U throw at me-?
If U die - (as a result of ELECTRICAL INCOMPETENCE)

It's a 100% fatality RATE.

Plus? I suppose U do HAVE "fire" insurence?
Which simply means ths...
Ur RISK is actually HIGHER than mine.

I have ZERO insurance... thus ZERO risk.

& finally...
U ARE WRONG... as it does NOT MATTER ... if you use an OLD sw or circuit breaker, NEW sw or circuit breaker...

IF U tease a "sw" ("precisely")...
IT IS POSSIBLE with ANY "switch" to create a delay_crossover function ... & thus an ARC (however minor)

The SNAP action- to which U refer- is the one the CIRCUIT BREAKER USES... & even "these" (NEW) can ARC severely... which is WHY they are specifically "built" with "extremely_efficient" (ANTI_ARC) suppression_chambers...

Assuming nothing has been changed the odds are he has a neutral fault that is common to all lights on that branch circuit. Likely in the switch box where power is brought first then onward to the other switches and lights. But could be in a receptacle box if power went to the switches and lights from it. He could narrow things down a tad if he removed light bulbs then tried the switches to see when the neutral fault showed itself with only one fixture with bulbs installed.

As for all the conversation from our friend in NZ ..120 volt single phase branch circuits do not react the same to arc flash as large switch gear in high voltage cabinets. It's like comparing apples to mangoes... or is it oranges...

RCD's cannot be compared to AFCI's. They can be compared to GFCI breakers to the extent of protecting one branch circuit. An RCD protects several branch circuits. Afci's if installed since 2005 are combination devices that detect both series and parallel arcs of the bad kind. Duration has a big play in a good and bad arc and current flow at the arc.. RCD's do not detect arcs. They only detect loss of current equalization between conductors in the branch circuit. Arcs do not always display themselves with minute current leakages to ground or neutral and therefore will not be detected by a RCD or GFCI which is our similar protective device.

Rather than me giving one of my famous always clear as mud dissertations I would suggest googling 'combination afci'. And spend some time reading. Square d offers a 'free' 10 minute training on afci if you want to order the product at no cost. They were sending it via e-mail but I'm not sure now what they do.

BTW the afci is very controversial at this time as most of us know and is not yet widely accepted by local jurisdictions, though more and more are requiring them.

For those interested here is a basic explaination of the combination afci now mandated by the national electrical code in the USA.

Stubbie - As for all the conversation from our friend in NZ ..120 volt single phase branch circuits do not react the same to arc flash as large switch gear in high voltage cabinets. It's like comparing apples to mangoes... or is it oranges...

KIWIS

Oh stop me, or I'll go too far....

__________________
If I could only remember to THINK about what I was doing before I did it.

Arch fault devise

Great forum, I am a woman sculptor and specialize in custom chandelier art, I am a UL certified engineer for luminairs. Recently a designer client emailed me with a bill (6 months after work was done and a year after fixtures were installed)for an electrician who switched out sockets on several of my fixtures claiming they were causing the new Arch fault devise to trip, the sockets, were brand new UL listed high quality Leviton, tested in my shop three times for shorts, damage and Hi-pot tested as well, fixtures passed. After emailing back and forth the electrician says the fixture worked fine but the light bulbs were not staying screwed in the socket "due to thermal shrinkage" which I find to be silly as I have been using these sockets for 10 years,

My UL inpector advised me to not pay the bill but get the old sockets back from client and send to manufacturer for a claim, client said work was dome months ago (they did not call me then of course) and sockets were gone. I do not feel resposible for the $1200 bill as this soulds like a faulty devise? Client is very upset and wants to pass the buck to me but even though they are a good client, I was not given a chance to inspect fixtures myself or even trouble shoot over the phone and I stand by the high quality of my work, paying would admit my fixtures were at fault.